Used fuel will be removed from the reactor and stored on site, and will be replaced with new fuel, Entergy spokesman Jerry Nappi said. Meanwhile, maintenance workers will perform hundreds of tests. The work will continue for three to four weeks, Nappi said.

"With Unit 3 shut down to be refueled, more than 2,000 workers will help perform hundreds of scheduled maintenance activities and inspections," said John Ventosa, an Entergy vice president, in a statement.

The power plant's remaining reactor, Indian Point 2, is operating at full capacity, Nappi said.